[论文解读] The Impact of Interpixel Capacitance on WFIRST PSFs

Arun Kannawadi, Charles Shapiro+4 more|arXiv (Cornell University)|Jun 29, 2018

CCD and CMOS Imaging Sensors参考文献 47被引用 1

一句话总结

本文研究了WFIRST近红外CMOS混合探测器中像素间电容（IPC）对点扩散函数（PSF）的畸变影响，导致PSF尺寸增大约5%，形状发生改变。通过基于物理原理的正向模拟，推导出一个线性拟合公式，用于量化因IPC可变性引起的PSF不确定性，这对弱引力透镜测量的准确性至关重要。

ABSTRACT

Unlike optical CCDs, near-infrared detectors, which are based on CMOS hybrid readout technology, typically suffer from electrical crosstalk between the pixels. The interpixel capacitance (IPC) responsible for the crosstalk affects the point-spread function (PSF) of the telescope, increasing the size and modifying the shape of all objects in the images while correlating the Poisson noise. Upcoming weak lensing surveys that use these detectors, such as WFIRST, place stringent requirements on the PSF size and shape (and the level at which these are known), which in turn must be translated into requirements on IPC. To facilitate this process, we present a first study of the effect of IPC on WFIRST PSF sizes and shapes. Realistic PSFs are forward-simulated from physical principles for each WFIRST bandpass. We explore how the PSF size and shape depends on the range of IPC coupling with pixels that are connected along an edge or corner; for the expected level of IPC in WFIRST, IPC increases the PSF sizes by ∼5\%. We present a linear fitting formula that describes the uncertainty in the PSF size or shape due to uncertainty in the IPC, which could arise for example due to unknown time evolution of IPC as the detectors age or due to spatial variation of IPC across the detector. We also study of the effect of a small anisotropy in the IPC, which further modifies the PSF shapes. Our results are a first, critical step in determining the hardware and characterization requirements for the detectors used in the WFIRST survey.

研究动机与目标

• 量化像素间电容（IPC）对WFIRST近红外探测器中点扩散函数（PSF）的影响。
• 确定IPC如何影响PSF尺寸和形状，这对弱引力透镜测量至关重要。
• 建立PSF测量不确定性模型，该不确定性源于探测器上IPC水平未知或随时间变化。
• 评估各向异性IPC对PSF形状畸变的影响。
• 基于PSF稳定性需求，为WFIRST探测器的硬件与校准要求提供基础依据。

提出的方法

• 针对每个WFIRST波段，从第一性物理原理出发正向模拟真实PSF。
• 在边缘和角落像素之间建模IPC耦合，以模拟串扰效应。
• 使用线性拟合公式，建立IPC不确定性与PSF尺寸和形状不确定性之间的关系。
• 分析IPC中微小各向异性对PSF形状的影响，尤其在弱引力透镜系统误差背景下的影响。
• 评估在WFIRST探测器预期IPC值范围内PSF尺寸和形状的变化。
• 量化IPC对PSF尺寸和形状的综合影响，包括噪声相关性效应。

实验结果

研究问题

• RQ1 像素间电容（IPC）如何影响WFIRST近红外探测器中PSF的尺寸和形状？
• RQ2 IPC使PSF尺寸增加的程度如何？这种影响在不同WFIRST波段中是否有所不同？
• RQ3 由于老化或空间分布差异导致的IPC不确定性，如何影响PSF测量的准确性？
• RQ4 各向异性IPC对PSF形状有何影响？它在弱引力透镜测量系统误差中起到何种作用？
• RQ5 线性模型能否准确描述IPC不确定性与PSF不确定性之间的关系？

主要发现

• 在预期的IPC水平下，像素间电容（IPC）使WFIRST的PSF尺寸增大约5%。
• IPC系统性地改变了PSF形状，微小的耦合各向异性的存在会引入额外畸变。
• 线性拟合公式能准确描述因IPC参数不确定性导致的PSF尺寸或形状不确定性。
• 由于IPC可变性引起的PSF测量不确定性必须在弱引力透镜校准中予以考虑，特别是针对时变或空间非均匀的IPC情况。
• 本研究提供了一个定量框架，可将PSF稳定性需求转化为WFIRST探测器的硬件与表征约束。
• 研究结果强调了精确表征和监测IPC的迫切需求，以满足弱引力透镜测量对PSF的严格要求。